Originally Posted by MattBeaty

The frictional force would not change, kinetic friction is defined as the coefficient of kinetic friction x the normal force. The coefficient of friction is derived from the properties of the materials (not changing, regardless of the size and shape of the brakes and pads) The normal force is simply the squeezing power of the brakes,, also doesn't change when the rotors size changes. The only difference is the lever warm, which is why the braking power increases. Also the increased mass would prevent overheating the brakes, but the main difference would be the increased lever arm.